The world's top climate scientists issued their final report on global warming on the weekend and the United Nations General Secretary says it makes for frightening reading.

The Intergovernmental Panel on Climate Change (IPCC) warns that the world is on the brink of an environmental catastrophe and calls for urgent action.

Australia's Prime Minister John Howard has moved to play down the concerns, promising the Coalition has a balanced approach to combating global warming.

But one Australian scientist who co-authored the IPCC reports says the only balanced approach is to cut emissions now.

UN representatives are known for using diplomatic language, but Secretary General Ban Ki-Moon has likened climate change to a horrifying science fiction movie. Even worse, because it is real.

"Ladies and gentleman, slowing and reversing these threats is the defining challenge of our age," he said.

In short, the IPCC's final report points to high average temperatures, melting glaciers and rising sea levels as the evidence.

The threat of climate change can no longer be ignored, because it has arrived. If the world does not act by cutting emissions, the panel warns, no country will be spared.

Famines will spread, water shortages will become more frequent, as will droughts and fierce storms.

Less than a week before the federal election, neither Labor nor the Coalition has committed to short-term emissions reductions.

Both major parties have debated climate change at length throughout the campaign, but scientists are passing that off as nothing more than baseless political rhetoric.

"This is a call to arms for the nation, a call to arms for the world to act now on climate change before it's too late," Labor leader Kevin Rudd said.

But Mr Howard says while his Government has a "sensible response", the report should not be taken out of context because "the world is not coming to an end tomorrow".

"You've got to have a common sense balanced approach," he said.

"We cannot ignore it, we have not ignored it, we have been dealing with it now for some years. We have got in place the building blocks of a sensible, rational, balanced response."

Affirmative action necessary

Former leader of the CSIRO's Climate Impact group, Dr Barrie Pittock, says Mr Howard's comments are non-committal and fail to appreciate the urgency of global warming.

"Well I think the Prime Minister's rhetoric sounds nice until you understand what it means, and what it means is they're not going to do anything for another 10 years, or nothing substantial," he said.

Dr Pittock, the author of two books on climate change and a contributor to all four of the IPCC's reports says the world can not afford to wait any longer.

"Climate change is definitely happening and in fact it's happening faster than the climate models were suggesting some years ago," he said.

"Since the cut-off date for published papers that IPCC has used, new papers have come out which show that the emissions and the concentrations of greenhouse gases and the global temperature and sea level are all increasing at the fastest of the rates that the IPCC thought was possible."

Dr Pittock says neither major political party has tackled the problem seriously enough during the election campaign, and says small incentives and multi-million-dollar packages hardly even begin to scratch the surface.

"But that compares with tens of billions of dollars in commitments for other things and I think they've got it completely out of proportion," he said.

Paying the price

Some 2,500 scientists worked on the IPCC's findings. The UN believes the worst case scenarios of global warming could be avoided if there were sharp reductions in greenhouse gas emissions.

The economic cost it argues, is minimal compared with the cost of doing nothing.

Professor Ove Hoegh-Guldberg is the Director of Marine Studies at the University of Queensland and also contributed to the IPCC report.

"The report points out that if we are going to avoid those catastrophic scenarios, we actually have to peak our emissions in 2015, which is just around the corner, eight years away," he said.

"Now to do that, we have to have really major efforts to change the way we use energy and we're going to have to have a range of international treaties in place not in 2012 but literally tomorrow."

Professor Hoegh-Guldberg says it is imperative that developed nations such as Australia and the US set an example by cutting emissions immediately through reducing energy needs, better insulation and construction standards and use of technology that currently exists, like solar energy.

"It's up to the developed countries to show some spine on this issue and avoid what will be a global catastrophe. It's relatively cost effective - in fact it's you know, really quite cheap - to address the issue and achieve that level of stabilisation.

"If we go down the street of trying to stabilise at about 450 parts per million, it will shave only, and this is an upper estimate, only about 0.12 per cent of the average annual growth in GDP."